Dr. Dick Swaab, a neuroscientist from Amsterdam University, says that women who smoke, drink or are under stress during their pregnancy are more likely to give birth to a baby that is gay.
According to the Science World Report the theory that Swaab proposed states that the lifestyle a woman choses to have while pregnant can effect the development of the baby. Swaab says that mothers who smoked during their pregnancy have a heightened chance of having a baby girl that is bisexual or lesbian.
The chance of a boy being gay depended highly on the number of older brothers that he had. The higher the number of brothers before, the more likely the child would be gay. Dr. Swaab believes very strongly that the sexuality of a child is determined in the womb and cannot be changed.
"Pre-birth exposure to both nicotine and amphetamines increases the chance of lesbian daughters," Swaab said. "Pregnant women suffering from stress are also more likely to have homosexual children of both genders because their raised level of the stress hormone cortisol affects the production of fetal sex hormones."
Swaab also claims that drinking and taking drugs while pregnant will lower a child's IQ later in life, according to The Telegraph, just as smoking and taking synthetic hormones can cause homosexuality.
The brain of a fetus begins to form two weeks into the pregnancy, after that any toxin put into the body will alter the child, according to Swaab's theory.
A baby's development is linked directly to his/her mother's lifestyle during pregnancy.